The machines for treating threads, used in the field of the textile industry, are often placed in a line to make possible different treatments of the textile threads continuously and thus to make possible a high yield resulting from a minimum number of interruptions of the process for production or treatment, for example for the sake of a machine change with modification of the speed of advance of the threads relative to the preceding or succeeding machines.
It is therefore advisable to ensure an intermediate storage of the threads to compensate for the speed differential that may exist between two thread treatment stations, so as to allow collision-free operation of a line for production and/or treatment.
For this purpose, a textile thread-accumulating device that uses a device for depositing threads in coils on the end of a longitudinal support and means for taking up said threads at the other end of this support is known by FR-A-2 576 885.
Such a device makes it possible to carry out a correct accumulation of threads, but it is not suitable for modern treatment and/or production lines whose very high operating speeds call for a significant accumulation capacity to take into account programmed cyclic interruptions or to make possible a smooth stopping of the line, i.e., with no significant impact requiring a very long reactivation time in the case of an accidental failure of a work station.
To prevent this drawback, it has been proposed to produce an accumulator device that consists essentially of a discharge chute, which, as an extension from the outlet, has an element for depositing a stranded-thread spiral, whose end that is opposite to the depositing element is guided in such a way as to be taken up and unwound by a downstream treatment or production station.
So as to regulate the speed and the tension of the strand during the unwinding, the discharge chute is equipped with a carriage that is guided parallel to the longitudinal axis of said discharge chute and that rests on the end of the strand of the side that is opposite to the depositing element, whereby this carriage is provided with strand guide means in the form of a guiding eyelet and/or a guiding and return bar. In addition, this carriage can be weighted in order to produce a support force on the head of the strand, at the outlet of the thread spiral, essentially to brake and monitor the strand during unwinding, i.e., to allow a certain tension of the thread spiral, as well as to obtain a predetermined strand density.
The devices of this type make possible, from the very fact of their constitution, an easy adaptation to the work conditions, i.e., that if a significant accumulation is to be produced, the only thing that needs to be done is to extend the discharge chute accordingly.
However, the accumulation devices of this type have the drawback of always having to be more or less inclined relative to the horizontal line to allow an effective action of the weighted carriage on the thread strand that is being formed and to ensure a correct tension of the thread spiral at the outlet of said carriage. In addition, taking into account this slope of the discharge chute, the vertical space that is occupied by these devices can become significant as the discharge chute is extended, and it then becomes necessary to provide for the operator elevated access means that extend over several levels, such as walkways, etc. High installation costs are the result.
In addition, the thread strand moves into the discharge chute by sliding into the latter and, starting from a certain length and based on the thread, the thus produced rubbing action against the wall of the discharge chute becomes significant, which, in combination with the action of the carriage, leads to an increase in the density of the strand.
This results in an impossibility of forming a homogeneous accumulation and a difficulty in taking up the thread spiral, such that the good operation of the treatment line may be affected. However, with the enhancement of the performance levels of the current treatment lines, the speed of taking up the threads increases proportionally and the adjustment of the take-up tension is difficult to carry out and takes too long because, to make this adjustment, the operator has to walk along the discharge-chute service walkway and install a ballast weight on the carriage. Consequently, the reaction time between the verification of a poor separation and the moment of the intervention that tends to modify the parameters of loads by means of the carriage is too long, and the action that is carried out runs the risk of being unsuitable.
In addition, the current increase of the speeds brings about a critical disadvantage for the safety of the operator. Actually, because of the tension of the threads, a break in the separation zone of the latter may have the consequence of forming a lasso-shaped loop that can hook onto the carriage, which can then be abruptly driven at the same speed as the threads and can be ejected from the discharge chute without the automatic safety devices being able to react.